This research project is concerned with the elucidation of the mechanism of physiologically important reactions. Two important objectives of this study are the detection of reaction intermediates and the delineation of elementary steps in complex biological processes. The particular types of biological systems under investigation include metabolic control through allosteric enzymes, organized enzymes, membrane-bound enzymes, and transport through membranes. Fast reaction techniques such as stopped-flow and temperature jump are utilized as well as more conventional equilibrium and kinetic methods. Fluorescence energy transfer and nuclear magnetic resonance measurements are used for structural mapping of macromolecular structures. A portion of this project is concerned with the improvement and development of physical methods which can be applied to biological systems.